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S. G. STARLING AND A. J. HUGHES.

MAGNETIC COMPAS S.

APPLIFATION FILED Hw- 25,1917

Patented June 24, 1919.

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s. e. STARLING AND ll; HUGHES. MAGNETIC COMPASS.

APFLHJAHON FILED 1AN.25.1917. 1,307,935. v Patented June 24,1919.

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MAGNETIC COMPASS.

APPLICATION FILED JAN-25' I917- I Patented June 24,1919.

s. e. STAR'LING Am) A. 1. HUGHES,

MAGNETIC COMPASS.

' APPLICATION-F|LED 1AN.25. 1911-. 1,307,935. Pa tentedJune 24 1919 4 SHEETS SHEET 4.

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STATES PATENT OFFICE.

SYDNEY enonen sTARLING, on ronnsr earn, AND amnion JOSEPH nuenns, on LoNDo ENGLAND, assemons 'ro HENRY HUGHES AND soN LTD or LoNDoN,

ENGLAND, a coaronArio or ENGLAND.

jivrnennrro oolvirAss.

To all whom it may concern: l

Be it known that we, SYDNEY Gnonen STARLING, of 61VVin dsor road, Forest Gate, in the county of Essex, England, and AR- THUR JosnPn: HUGHES, of 59 Fenchurch street, in the city and county of London, England, both subjects of theKing ofGreat Britain, have invented anewand usefullmprovement in y and Relating to Magnetic Compasses, of which the following is a speclfication. i

This invention relates to magnetic com passes more particularly for use on aircraft This is to distinguish it from a quadrantal" error which changes signevery 90 of rotation. Semi-circular error in a ship is due to permanent magnetization andgalso to vertically disposed soft iron. In an'aeroplane it is chiefly due to the vertical component of the earths magneticfield. The error due to the vertlcal component is the more m1 portant. These errors are rectified or 1n1n1'- mized by the present invention.

According to this invention the semi-circular error is corrected by producing a magnetic field which is vertical when the compass card is in the normal orrest position,

said field being produced by means of vertically disposed magnets. In order to ob tain a component of the magnetic field in the plane of the cardin a direction opposlte to the component of the earths vertical field 111 that plane when the compass card is tllted, means are provided for tilting the magnets in the same or the opposite direction to the tilting of the compass card. A similar result may be obtained by raising one magnet and depressing the other.

For correcting quadrantal error provision ,is-made for varying the distance of soft iron Specification of Letters Patent. i

Patented June 24, 1919.

5 Application filed January 25, 1917. Serial No.144,521.

masses from the compass bowl as the tilt changes in turning. i The accompanying drawings are illustrative of my invention- 1 Figure 1 beinga front view and Fig. 2 a plan view of one mode of correcting the se1ni-circular error according to this invention. 1 i s i Figs. 8 and 1 are respectively a front view and an inverted plan view of a modification.

Figs. 5 and 6 illustratethe means for correcting the quadrantal error according to this invention. i

Incarrying out the invention andto correct the semi-circular error, the magnets 1, 1, are mounted vertically on a f 'aine orholder Qcapable of rotating about an axis. parallel to the fore and aftline of the aeroplane or other craft andpassing through the center of the compass card mounted in the compass a, as'illustrated in Figs. 1 and 2. The

frame or holder comprises a ring 2 which embraces theufront portion of the compass case a and is supported upon the latter by means of studs 2 which,however, do not enterthe compass casebut are free to more around the latter. Extending laterally from thering- Qtare the arms2 which support the magnets 1. The [frame and magnets may be rotated by means such as shown 111 Fig. 3

and comprising wires or cords 3, 3 passing over pulleys a, 5, the cord?) being connected with the steering gear, or beingoperated by a stabilizer or by hand. The cord 3 is connected to the lnagnets 1 supported by the coil springs 1", both springs and magnets .belng mounted in the casings 1. i The magnets may have their N poles upward, in whlch case the attachments of the cords should be so arranged that the tilt of the magnets is in the same direction as the tilt of the aeroplane. On the other hand, if the N poles of the magnets are downward, the attachment of the cords should be so arranged that the magnets rotate in the oppositeidirectio-n to the tilt of the machine. In

either case, the field due to the magnets is adjusted by altering the distance of the magnets or otherwise, until its strength at the compass card is as nearly as possible equal to thevertical component of the earths magnetic field, thus correcting the semi-circular error. The points of attachment of the cord to the steering gear or to the stabilizer are found by trial and are so disposed as to cause the magnets to tilt with respect to the aeroplane to an extent which is approximately equal to the inclination of the aeroplane to the horizontal. The magnets then introduce a component of magnetic field in the plane of the compass card, equal and opposite to that of the resolved part of the earths magnetic field in the plane of the card which latter produces the disturbance.

We employ magnets and produce the correcting field by raising one magnet and lowering the other. This could be accomplished by connecting the magnets l, 1, together by means of the cord 3 which is passed over guide pulleys 1 at the ends of the magnet casing 1 and then over the pulley 4 as shown in Fig. 3. The magnets 1, 1, are supported upon helical springs 1h so that when the pulley 1 is rotated the cord 3 pulls down one magnet and releases the other which rises under the influence of its spring. In this case the magnets are not rotated above the compass case but are moved vertically in opposite directions.

To correct both the quadrantalerror due to the earths horizontal component and the semi-circular error, soft iron is employed in conjunction with the magnets shown in Figs. 1 and 2 or Figs. 3 and 1. To enable the intensity of the field to be varied as the tilt changes, a pair of soft iron bars 6, 6, may be employed, as shown in Figs. 5 and 6, and be placed under or over the compass bowl a. These bars are carried by arms which are hinged together at one end and are attached to the steering gear by means of a cord in such a manner that the ends of the arms carrying the soft iron bars 6 are raised as the tilt increases.

According to the construction illustrated in Figs. 5 and 6, the soft iron correctors 6, 6, are-mounted upon arms 7, 7 ,which are pivotally mounted upon a vertical standard 8. The ends of the arms 7, 7, are connected by means of links 9, 9 to a pin 10 mounted in a rod 10 and working in slots 11 formed in the standard 8. The rod 10 is connected by the part 12 with the operating device not shown, and as the latter is operated the links 9 are drawn together to close the correctors 6, 6, toward the compass bowl. Springs 13 draw the arms 7 and the links 9 together to separate the correctors from the compass bowl.

hat we claim as our invention and de sire to secure by Letters Patent, is

1. The herein described mode of correcting semi-circular errors in a magnetic compass due to lateral turning movements, which consists in producing a magnetic field, the component of which in the plane of the card is in a direction opposite to the component of the earths vertical field in that plane, substantially as described.

2. For correcting errors in a magnetic compass on an aeroplane, due to lateral turning I movements, the combination with a compass,

of a frame projecting on opposite sides of said compass, vertical magnets mounted upon said frame on opposite sides of the compass, with means for moving said magnets controlled incident to the operation of the aeroplane, substantially as described.

3. For correcting quadrantal errors in a magnetic compass on an aeroplane, due to lateral turning movements, a pair of soft iron correctors and means controlled incident to the operation of the aeroplane, whereby the correctors are drawn toward or away from the compass bowl, with change in the control of the aeroplane, thereby varying the intensity of the field, substantially as described.

SYDNEY GEORGE STARLING. ARTHUR JOSEPH HUGHES.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents,

' Washington, D. G. 

